Since most film supports used in the practice of preparing photosensitive elements are comprised of polymeric shaped supports and these have a high dielectric constant, they exhibit a propensity to produce static during use. Static will yield unwanted exposure of the photosensitive layers associated with such supports and cannot be tolerated. It is well-known to prepare antistatic compositions containing antistatic agents and other components and to coat these compositions in layers on the film supports during the preparation of the photographic element. One such antistatic composition is described by Schadt, III, U.S. Pat. No. 4,225,665. A description of the associated state of the art related to this field is contained in this reference.
Although the Schadt, III composition and associated layers made therefrom is adequate in preventing static within the photographic element, Schadt, III suffers from some disadvantages which prevent full utilization of his system. One disadvantage is that the Schadt, III layers must be coated to a rather thick coating weight which adds to the coating cost and increases inherent light scattering or haze in the element thereby reducing the clarity and usefulness of photographic elements made therefrom. Haze is particularly onerous when associated with elements wherein the antistatic layer is not overcoated with a silver halide emulsion or gel layer. Another disadvantage of Schadt, III is that a multicomponent system is used, including a binding agent and a crosslinking agent in addition to the antistatic agent, whereby premature crosslinking can occur prior to coating.
In assignee's copending Miller application U.S. Ser. No. 875,251, filed June 17, 1986, now U.S. Pat. No. 4,701,403, based on U.S. Ser. No. 691,768, filed Jan. 16, 1985, now abandoned, there is described an improvement over Schadt, III in which the components are segregated and the crosslinking agent coated as a separate layer. Miller found that when a composition containing antistatic agent and crosslinking agent with and without a binding agent are coated as a single layer the physical and electrical permanence is reduced. The process described by Miller allows the coating of overall thinner antistatic layers, prevents premature crosslinking of associated polymeric materials and provides physical and electrical permanence. However, the Miller process requires a two step coating which requires additional investment and operating cost.
It is desired to provide in a photographic element a relatively thin layer which will yield more permanent antistatic properties, improved optical properties, and maintain the clarity of the final element made therefrom.